Low fraction of methane in landfill gas emissions in an industrial waste landfill containing incineration ash and gypsum board waste under anaerobic conditions

摘要

The behaviour of carbon dioxide (CO_2) and methane (CH_4) emissions at the surface and below the soil cover in an industrial waste landfill under anaerobic operating conditions was evaluated for six years. This landfill contained gypsum board waste and incineration ash - a practice currently allowed because of a change in Japanese regulations. The CO_2 and CH_4 fluxes decreased throughout the six years of the survey. Almost all of the survey points exhibited fractions of CH_4 in landfill gas emissions of ＜0.5 (mean values: 0.0-0.1 [surface], 0.0-0.3 [subsurface]) under anaerobic conditions. In addition, a relatively high first-order reaction rate constant for the landfill gas emissions (0.3 year~(-1)) was observed. The landfill leachate showed a relatively high sulphate ion (SO_4~(2-)) concentration, although other environmental conditions, such as the pH, oxidation-reduction potential and ammonium concentration, were not at levels that could have inhibited CH_4 production. These findings suggest that the low fractions could have been related to the lower amounts of CH_4 generation caused by competition between methanogens and sulphate-reducing bacteria (SRB). Therefore, SRB could play a major role in the degradation of organic carbon in the landfill.